1. Field of the Invention
This invention pertains generally to waveguide antenna devices and methods for propagation of RF energy. More particularly, the invention is a rectangular waveguide antenna apparatus having a continuous slot aperture, a variable height, variable width internal ridge, and a constant external cross section.
2. Description of the Background Art
Numerous types of waveguides are utilized for propagation of electromagnetic energy, typically in the frequency range of between 1 and 150 GHz. Different waveguide cross-sectional shapes and dimensions are selected for distinct electromagnetic field configurations or modes. Rectangular waveguides are widely used for propagation of the transverse electric or TE.sub.10 mode. In order to optimize the propagation and phase characteristics of waveguides for optimal energy transfer, designers often must use waveguide shapes and dimensions which are difficult and expensive to manufacture, which cause difficulty in mounting the waveguide, or which result in high losses.
U.S. Pat. No. 4,328,502 to Scharp discloses an antenna consisting of a single continues curved-slot in the broad face of a rectangular waveguide which is useful in reducing radiation pattern beamwidth and extending the range of overall slot length. U.S. Pat. No. 4,330,784 to Ryno et al discloses an antenna which is a continuous slot antenna having a rectangular waveguide whose broad dimension varies in proportion to the attenuation for providing an improved radiation pattern. While the antennas disclosed in these patents provide for an enhanced radiation pattern and, in particular, a means for amplitude control of the radiated energy, there is still a need for a waveguide apparatus which allows for independent control of the phase of the radiation pattern while maintaining the rectangular shape of the waveguide.
In addition, there is a need for an antenna having a shape and dimensions which facilitate manufacture and mounting, which allows for accurate control of the propagation constants, and which has low losses. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in the background art.